1. Field of the Invention
The invention relates to a technology for cooling an electronic device, and more particularly to a technology for cooling an electronic device based on its surface temperature predicted in advance.
2. Description of the Related Art
Electronic equipment is controlled by various types of electronic devices such a CPU (Central Processing Unit) and a DSP (Digital Signal Processor), which are made of various electronic components including active elements such as a transistor and passive elements such as a capacitor. Part of electric energy for driving these electronic components is converted into thermal energy and dissipated as heat. The performance of the electronic components typically has temperature dependence. Then, the dissipated heat has an effect on the performance of the electronic components, and by extension that of the electronic devices. Technologies for cooling the electronic devices are thus of significant importance in controlling the electronic devices properly.
An example of the technologies for cooling the electronic devices is an air cooling method which uses electric fans. In this method, for example, an electric fan is arranged opposite to the surface of an electronic device. Cool air is sucked from an air inlet and blown onto the surface of the electronic device by the electric fan. The air is warmed by absorbing heat occurring from the surface of the electronic device, and is emitted from an air outlet. In this way, the heat occurring from the surfaces of the electronic devices is exhausted by electric fans, whereby the electronic devices are cooled.
Devices intended for heat dissipation, called heat sinks, are also used commonly. In order to transfer heat from the heat source such as an electronic device to surrounding cool fluid or air efficiently, heat sinks are usually designed to have large areas of heat transfer. The heat caused by an electronic device is transferred to a heat sink, and is dissipated through the large area of heat transfer of the heat sink.
This method of using an electric fan and a heat sink in combination is the technique that is commonly used for cooling a semiconductor chip.
Temperature changes of the foregoing electric fans and heat sinks typically have considerably poor time responses as compared to variations in the amounts of heat to be generated by the electronic devices. In other words, these conventional cooling methods have had difficulties in cooling the electronic devices efficiently since the amounts of heat generated by the electronic devices can vary with time. To ensure the reliability of operation of the electronic devices, it is therefore necessary to provide margins for cooling power. There have thus been the problems that the electric fans grow in power consumption and noise, and that the electric fans must have excessively large volumes.